1. Field of the Invention
The present invention relates to a process for producing an iron oxide used for a magnetic recording medium. More particularly, it relates to a process for producing a magnetite powder which imparts superior magnetic characteristics by reducing an iron oxide powder without sintering under high chemical stability even at high temperature.
2. Description of the Prior Arts
The inventors have found a process for producing magnetite powder having excellent magnetic characteristics especially coercive force by reducing an iron oxide powder with an inert gas containing a vapor of a lower alcohol instead of hydrogen gas as a reducing agent so as to prevent sintering in the reaction and to perform a stable reducing reaction which is disclosed in Japanese Examined Patent No. 24637/1978.
In the former process, the reduction temperature is limited to 450.degree. C. When it is higher than 450.degree. C., the reducing reaction is excessively performed to reduce a portion of magnetite into metallic iron or the sintering is resulted to cause the unstable condition of the reaction system. As a result, magnetic characteristics of magnetite as the product or .gamma.-iron oxide obtained by oxidizing it are deteriorated.
In a reducing reaction, the reaction is completed for shorter time with higher thermal efficiency at higher temperature. Therefore, it is preferable to perform the reducing reaction at higher temperature.
The inventors have studied to improve the former process for producing magnetite as a magnetic recording medium so as to prevent said disadvantages.